Sound absorbing structure and tire

Abstract

This sound absorbing structure comprises: a box body having an opening; and a hollow neck part communicating with the opening and extending to a hollow part side of the box body, wherein the opening is formed in a side part of the box body. This tire includes the sound absorbing structure attached to an internal cavity part.

Description

Sound-absorbing structure and tire

[0001] The present disclosure relates to a sound absorbing structure and a tire.

[0002] Patent Document 1 describes a sound-absorbing structure that reduces vibrations within a cavity by Helmholtz resonance. This sound-absorbing structure is attached to the tire cavity to reduce tire cavity resonance noise generated when a vehicle is running. This sound-absorbing structure has an auxiliary chamber forming portion that forms an auxiliary chamber and has an opening formed therein.

[0003] Japanese Patent Application Laid-Open No. 2021-067767

[0004] Tire cavity resonance noise generated when a vehicle is running is in the low-frequency band, for example, around 200 Hz to 300 Hz. The sound-absorbing structure described in Patent Document 1 can reduce such low-frequency resonance noise by increasing the length of the opening. However, the opening is formed in the top part of the auxiliary chamber forming portion facing the radial center of the tire and extends in the thickness direction of the sound-absorbing structure. Therefore, increasing the length of the opening poses the problem of increasing the thickness of the sound-absorbing structure. If the sound-absorbing structure becomes thicker, it will become larger, which may obstruct the airflow in the tire cavity. Furthermore, the sound-absorbing structure will become heavier, which may lead to a decrease in the rotational balance of the tire.

[0005] The present disclosure aims to provide a sound-absorbing structure that can easily be made thinner while reducing resonance noise in the low-frequency range, and a tire equipped with this sound-absorbing structure.

[0006] The sound-absorbing structure of the present disclosure comprises a box body having an opening and a hollow neck portion that is connected to the opening and extends toward the hollow portion of the box body, and the opening is formed in the side of the box body.

[0007] This sound-absorbing structure includes a box body having an opening and a hollow neck portion that is connected to the opening and extends toward the hollow portion of the box body. This allows the sound-absorbing structure to function as a Helmholtz resonator, and by lengthening the neck portion, it is possible to generate Helmholtz resonance at a resonant frequency in the low-frequency range. The opening is formed on the side of the box body and is oriented in a direction intersecting the thickness direction of the sound-absorbing structure. This makes it easy to extend the neck portion connected to the opening in a direction intersecting the thickness direction of the sound-absorbing structure. In other words, the neck portion can be lengthened without increasing the thickness of the sound-absorbing structure. This makes it easy to reduce the thickness while reducing low-frequency resonant noise.

[0008] In the above-described sound absorbing structure, the side portions may extend in a direction intersecting with a direction orthogonal to the thickness direction of the sound absorbing structure. In this sound absorbing structure, since the side portions extend in a direction intersecting with a direction orthogonal to the thickness direction of the sound absorbing structure, it is possible to easily reduce the thickness of the sound absorbing structure.

[0009] In the above-described sound absorbing structure, the neck portion may extend in a direction perpendicular to the thickness direction. In this sound absorbing structure, since the neck portion extends in a direction perpendicular to the thickness direction, it is possible to reduce the thickness of the sound absorbing structure while reducing resonance sounds in the low frequency range.

[0010] In the above-described sound-absorbing structure, the neck portion may have a fixing portion that is fixed to the box at a position spaced apart from the opening. In this sound-absorbing structure, the neck portion has a fixing portion that is fixed to the box at a position spaced apart from the opening, thereby suppressing movement of the neck portion relative to the box. Therefore, for example, when an external force such as centrifugal force or vibration acts on the sound-absorbing structure, excessive displacement of the neck portion relative to the box can be suppressed.

[0011] In the above-described sound absorbing structure, the opening may be a circular hole. In this sound absorbing structure, the opening is a circular hole, which makes it easy to design it as a Helmholtz resonator.

[0012] In the above-described sound absorbing structure, the opening may be a linear slit. In this sound absorbing structure, the opening is a linear slit, which makes it easy to manufacture the sound absorbing structure.

[0013] The sound absorbing structure described above may further include a porous sound absorbing material housed in the hollow portion of the box. By including the porous sound absorbing material, this sound absorbing structure can reduce sounds in the high frequency range.

[0014] In the above-described sound absorbing structure, the box may have at least one of a Shore A hardness of 40 to 100 and a Shore D hardness of 10 to 70. In this sound absorbing structure, by having the box have at least one of a Shore A hardness of 40 to 100 and a Shore D hardness of 10 to 70, deformation due to external forces such as centrifugal force and vibration can be suppressed, while the conformability to the surface to which the box is attached can be improved.

[0015] In the sound-absorbing structure described above, the box may contain an elastomer, which can improve conformability to the surface to which the sound-absorbing structure is attached while suppressing deformation due to external forces such as centrifugal force and vibration.

[0016] In the above-described sound-absorbing structure, the box body may have a top portion, and the side portions may be connected to the peripheral edge of the top portion and extend in a direction intersecting the extending direction of the top portion. In this sound-absorbing structure, the box body has a top portion and side portions connected to the peripheral edge of the top portion and extending in a direction intersecting the extending direction of the top portion, so that the top portion can cover the upper part of the hollow portion.

[0017] In the above-described sound-absorbing structure, the box may further have a bottom connected to the side and facing the top. In this sound-absorbing structure, the box has a bottom connected to the side and facing the top, which allows the sound-absorbing structure to function as a Helmholtz resonator by itself. Therefore, even if a gap occurs between the sound-absorbing structure and the surface to which it is attached, the sound-absorbing structure can still function as a Helmholtz resonator.

[0018] In the above-described sound-absorbing structure, the box may have a plurality of openings and partition walls connected to the top and side walls that divide the hollow space into two small spaces, and the partition walls may divide the hollow space such that at least one opening is in communication with each of the two small spaces. In this sound-absorbing structure, by dividing the hollow space of the box into two small spaces by the partition walls and by having at least one opening in communication with each of the two small spaces, it is possible to increase the rigidity of the sound-absorbing structure while allowing each of the two small spaces to function as a Helmholtz resonator.

[0019] In the above-described sound-absorbing structure, the partition wall may divide the hollow portion into two small spaces, each of which has one opening communicating with the other. In this sound-absorbing structure, by having one opening communicating with each of the two small spaces, the sound-absorbing structure can be divided into Helmholtz resonator units.

[0020] In the above-described sound-absorbing structure, the partition wall may have a first partition wall portion located on one side of the two small spaces and a second partition wall portion located on the other side of the two small spaces, and the top and side portions may be divided by the first and second partition wall portions. In this sound-absorbing structure, because the top and side portions are divided by the first and second partition wall portions, the sound-absorbing structure can be easily curved or bent, thereby further improving its ability to conform to the surface to which it is attached.

[0021] In the above-described sound absorbing structure, the first partition wall portion and the second partition wall portion may be arranged so that the distance between them increases toward the top. In this sound absorbing structure, the first partition wall portion and the second partition wall portion are arranged so that the distance between them increases toward the top, making it easier to curve or bend the sound absorbing structure so that the top surface faces inward.

[0022] In the above-described sound absorbing structure, the first partition wall portion and the second partition wall portion may be connected to each other at their ends opposite the top portion. In this sound absorbing structure, the first partition wall portion and the second partition wall portion are connected to each other at their ends opposite the top portion, which allows the sound absorbing structure to bend or curve while preventing the sound absorbing structure from becoming large.

[0023] A tire according to the present disclosure includes any one of the above-described sound-absorbing structures attached to the tire cavity. Because this tire includes the above-described sound-absorbing structure, it is possible to reduce the thickness of the sound-absorbing structure while reducing low-frequency resonance noise. By reducing the thickness of the sound-absorbing structure, for example, it is possible to prevent the sound-absorbing structure from interfering with the airflow in the tire cavity and to prevent the sound-absorbing structure from impairing the tire's rotational balance.

[0024] In the above-described tire, the sound absorbing structure may be provided with a Helmholtz resonance structure that generates Helmholtz resonance with a resonance frequency within a range of ±100 Hz of the frequency of tire cavity resonance noise calculated from F = c / ((R + r) × π), where F is the frequency of tire cavity resonance noise, c is the speed of light, R is the radius of the tire cavity, r is the radius of the rim of a wheel mounted on the tire, and π is the ratio of the circumference of a wheel to its circumference. Because this tire is provided with a Helmholtz resonance structure that generates Helmholtz resonance with a resonance frequency within a range of ±100 Hz of the frequency of tire cavity resonance noise, it is possible to reduce tire cavity resonance noise.

[0025] According to the present disclosure, it is possible to easily reduce the thickness while reducing resonance noise in the low frequency range.

[0026] FIG. 1 is a schematic cross-sectional view of a tire equipped with a sound absorbing structure according to a first embodiment. FIG. 2 is a schematic perspective view of the sound absorbing structure according to the first embodiment. FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a schematic cross-sectional view of the sound absorbing structure according to a second embodiment. FIG. 5 is a schematic cross-sectional view of the sound absorbing structure according to a third embodiment. FIG. 6 is a schematic cross-sectional view of the sound absorbing structure according to a fourth embodiment. FIG. 7 is a schematic cross-sectional view of the sound absorbing structure according to a fifth embodiment. FIG. 8 is a schematic perspective view of the sound absorbing structure according to a sixth embodiment. FIG. 9 is a schematic cross-sectional view taken along line IX-IX in FIG. 8. FIG. 10 is a schematic perspective view of the sound absorbing structure according to a seventh embodiment. FIG. 11 is a schematic cross-sectional view taken along line XI-XI in FIG. 10. FIG. 12 is a schematic cross-sectional view taken along line XII-XII in FIG. 10. FIG. 13 is a schematic perspective view of the sound absorbing structure according to an eighth embodiment. Fig. 14 is a schematic cross-sectional view taken along line XIV-XIV shown in Fig. 13. Fig. 15 is a schematic perspective view of a sound absorbing structure according to a ninth embodiment. Fig. 16 is a schematic side view of a sound absorbing structure according to a modified example. Fig. 17 is a diagram showing a method for calculating the resonant frequency of a Helmholtz resonance structure.

[0027] Hereinafter, an embodiment of a sound-absorbing structure according to the present disclosure will be described in detail with reference to the drawings. In this embodiment, the sound-absorbing structure according to the present disclosure is applied to a tire sound-absorbing structure that is attached to the tire cavity in order to reduce tire cavity resonance noise. In the drawings, the same or corresponding parts are designated by the same reference numerals, and duplicate explanations will be omitted.

[0028] First Embodiment Fig. 1 is a schematic cross-sectional view of a tire equipped with a sound-absorbing structure according to a first embodiment. In a tire 101, cavity resonance can occur, in which the air inside the tire resonates due to vibrations caused by passing over uneven road surfaces while the vehicle is traveling. The frequency of sound caused by cavity resonance is approximately 200 Hz to 300 Hz, typically approximately 250 Hz. The sound-absorbing structure 1 according to this embodiment is attached to an inner cavity 102 of the tire 101 in order to efficiently absorb low-frequency sound caused by cavity resonance. The inner cavity 102 is the inner circumferential surface of a tread 103.

[0029] A sound-absorbing structure 1 according to a first embodiment will be described with reference to FIGS. 2 and 3 . FIG. 2 is a schematic perspective view of the sound-absorbing structure according to the first embodiment. FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. 2 . As shown in FIGS. 1 to 3 , the sound-absorbing structure 1 according to this embodiment is a thin sound-absorbing structure equipped with a Helmholtz resonance structure. The sound-absorbing structure 1 being equipped with a Helmholtz resonance structure means that the sound-absorbing structure 1 alone generates Helmholtz resonance, or that the sound-absorbing structure 1 generates Helmholtz resonance when attached to the inner cavity 102 of the tire 101. The sound-absorbing structure 1 includes a mounting surface 2 that is attached to the inner cavity 102 of the tire 101, and a top surface 3 that is disposed opposite the mounting surface 2. For example, an adhesive sheet 4 is attached to the mounting surface 2 to mount the sound-absorbing structure 1 to the inner cavity 102 of the tire 101.

[0030] The sound-absorbing structure 1 is formed in a rectangular strip shape. The direction in which the mounting surface 2 and the top surface 3 face each other is referred to as the thickness direction D1 of the sound-absorbing structure 1. As is clear from FIGS. 1 to 3 , the thickness direction D1 of the sound-absorbing structure 1 is also the height direction (thickness direction) relative to the mounting surface 2. Furthermore, the thickness direction D1 of the sound-absorbing structure 1 is also the height direction (thickness direction) relative to the inner cavity 102 of the tire 101 when the sound-absorbing structure 1 is attached to the inner cavity 102. The sound-absorbing structure 1 is formed in a rectangular shape when viewed from a plan view in the thickness direction D1. Of the directions perpendicular to the thickness direction D1, the longitudinal direction of the sound-absorbing structure 1 is referred to as the length direction D2, and the lateral direction of the sound-absorbing structure 1 is referred to as the width direction D3. The thickness T2 of the sound-absorbing structure 1 is, for example, 20 mm or less. The thickness T2 is the dimension in the thickness direction D1. The width W1 of the sound-absorbing structure 1 is, for example, approximately 30 mm or more and 40 mm or less. The width W1 is the dimension in the width direction D3. The length of the sound absorbing structure 1 is, for example, about 30 mm to 2000 mm. The length of the sound absorbing structure 1 is the dimension in the length direction D2.

[0031] The sound absorbing structure 1 is configured to include a box body 10 and a plurality of neck portions 20.

[0032] The box body 10 is a box-shaped member having a hollow portion 11 therein. The box body 10 forms the outer shape of the sound-absorbing structure 1. The box body 10 is also called a skin. The box body 10 has a plurality of openings 12 that communicate with the hollow portion 11. The openings 12 penetrate the box body 10 and serve as entrances for tire cavity resonance noise. The shape (cross-sectional shape) of the openings 12 is not particularly limited and can be various shapes such as circular, triangular, rectangular, polygonal, and elliptical. In this embodiment, the openings 12 are circular holes that penetrate the box body 10. In other words, the cross-sectional shape of the openings 12 is circular. The inner diameter of the openings 12 is, for example, approximately 1 mm to 5 mm. The number of openings 12 in the box body 10 is not particularly limited.

[0033] The box body 10 is non-breathable. The box body 10 has at least one of a Shore A hardness of 40 to 100 and a Shore D hardness of 10 to 70. In this case, the Shore A hardness of the box body 10 may be 50 to 80 or 60 to 70. The Shore D hardness of the box body 10 may be 10 to 50 or 10 to 40.

[0034] The Shore A hardness of the box body 10 can be measured using a durometer in accordance with JIS K6253-3, for example, a GS-709N TYPE A manufactured by Teclock Corporation can be used. The Shore D hardness of the box body 10 can be measured using a durometer in accordance with JIS K6253-3, for example, a GS-720N TYPE D manufactured by Teclock Corporation can be used. If the allowable number of stacked test pieces specified in JIS K6253-3 (three or less) does not satisfy the specified measurement thickness (6 mm or more), more than three pieces can be stacked and the measurement can be performed at the specified thickness.

[0035] The material of the box 10 includes, for example, an elastomer such as a thermoplastic elastomer, a plastic, a rubber, a rubber-like material, or other resin.

[0036] Examples of elastomer materials include thermoplastic elastomers such as styrene block copolymer (SBC), polyolefin (TPO), polyurethane (TPU), polyester (TPC), polyamide (TPA), dynamically crosslinked (TPV), soft polyvinyl chloride (PVC), and acrylic.

[0037] Examples of plastic materials include polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), acrylonitrile butadiene styrene (ABS), polyphenylene sulfide (PPS), polyurethane (PU), epoxy resin, phenolic resin, and melamine resin.

[0038] Examples of rubber materials include natural rubber (NR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), silicone rubber, and urethane rubber.

[0039] Examples of rubber-like materials include UV-curable acrylic rubber-like materials.

[0040] The box 10 includes a top portion 13, side portions 14, and a bottom portion 15. The box 10 has a thickness T1 of, for example, about 0.1 mm to 2 mm. That is, the thickness T1 of each of the top portion 13, side portions 14, and bottom portion 15 is, for example, about 0.1 mm to 2 mm.

[0041] The top portion 13 is a portion that forms the top surface 3. The top portion 13 covers the upper side of the hollow portion 11. The upper side of the hollow portion 11 is one direction in the thickness direction D1. The top portion 13 is formed in a substantially rectangular shape in a plan view seen from the thickness direction D1.

[0042] The side portions 14 are portions that form part of the mounting surface 2. The side portions 14 are connected to the peripheral edge of the top portion 13 and extend in a direction intersecting the extension direction of the top portion 13. The extension direction of the top portion 13 is a direction along the length direction D2 and the width direction D3. Here, the direction along the length direction D2 and the width direction D3 is a direction perpendicular to the thickness direction D1, so the side portions 14 extend in a direction intersecting the direction perpendicular to the thickness direction D1. The direction intersecting the extension direction of the top portion 13 refers to, for example, a direction that does not coincide with the length direction D2 and the width direction D3 and is inclined at an angle greater than 0° with respect to the length direction D2 and the width direction D3. For example, the thickness direction D1 and a direction inclined with respect to the thickness direction D1 are also included in the direction intersecting the extension direction of the top portion 13.

[0043] The side portions 14 cover the sides of the hollow portion 11. The sides of the hollow portion 11 are the directions along the length direction D2 and the width direction D3. The side portions 14 extend from the peripheral edge of the top portion 13 to the mounting surface 2 around the entire circumference of the top portion 13. A cross section of the side portions 14 perpendicular to the thickness direction D1 is formed in the shape of an endless rectangular ring. The side portions 14 have, for example, a tapered shape that narrows toward the top portion 13. In other words, the side portions 14 are inclined with respect to the thickness direction D1 so as to widen from the top portion 13 toward the mounting surface 2. The inclination angle θ of the side portions 14 with respect to the thickness direction D1 is, for example, approximately 0° or more and 50° or less.

[0044] The side portions 14 have a pair of long side portions 141 that extend in the length direction D2 and face the width direction D3, and a pair of short side portions 142 that extend in the width direction D3 and face the length direction D2. The pair of long side portions 141 and the pair of short side portions 142 are connected to each other at both end edges.

[0045] A plurality of openings 12 are formed in the side portion 14, penetrating the side portion 14 and communicating with the hollow portion 11. In this embodiment, the plurality of openings 12 are formed in one of the long side portions 141 and are aligned in a row in the longitudinal direction D2. The long side portion 141 in which the plurality of openings 12 are formed is referred to as the opening-forming side portion 143. The opening ratio of the openings 12 in the opening-forming side portion 143 (the ratio of the total area of ​​the openings 12 to the area of ​​the opening-forming side portion 143 on the surface of the opening-forming side portion 143) is, for example, approximately 0.1% to 10%.

[0046] The bottom portion 15 is a portion that forms part of the mounting surface 2. The bottom portion 15 is connected to the side portion 14 and faces the top portion 13. The bottom portion 15 covers the lower portion of the hollow portion 11. The lower portion of the hollow portion 11 is the other direction in the thickness direction D1, that is, the direction opposite to the upper portion of the hollow portion 11.

[0047] The neck portion 20 is a hollow member that communicates with the opening 12 and extends from the opening-forming side portion 143 toward the hollow portion 11. The base end of the neck portion 20 is connected to the opening 12. The tip of the neck portion 20 is an open end that exposes the hollow portion S of the neck portion 20 and is located within the hollow portion 11. The neck portion 20 is formed, for example, integrally with the box body 10. The number of neck portions 20 is the same as the number of openings 12, and each neck portion 20 is connected to one of the openings 12.

[0048] The neck portion 20 is non-breathable like the box body 10. The neck portion 20 has at least one of the Shore A hardness and the Shore D hardness similar to that of the box body 10. The material of the neck portion 20 can be the same as the material of the box body 10.

[0049] The hollow portion S of the neck portion 20 has a cross section that is the same as or larger than the cross section of the opening 12. By increasing the extension length of the neck portion 20, the resonance frequency of the sound absorbing structure 1, which functions as a Helmholtz resonator, can be reduced. In other words, by increasing the extension length of the neck portion 20, resonance sounds in the low frequency range can be reduced. The tip of the neck portion 20 on the opening 12 side is referred to as the base end, and the tip of the neck portion 20 on the opposite side of the opening 12 is referred to as the tip. The extension length of the neck portion 20 is the length of the extension axis of the neck portion 20 from the base end on the opening 12 side to the tip on the opposite side of the opening 12.

[0050] The shape of the neck portion 20 is not particularly limited. For example, the neck portion 20 may extend linearly from the opening 12 in the width direction D3. Here, the width direction D3 is a direction perpendicular to the thickness direction D1. Therefore, "the neck portion 20 extending from the opening 12 in the width direction D3" means that the neck portion 20 extends in a direction perpendicular to the thickness direction D1 of the sound-absorbing structure 1. "The neck portion 20 extending linearly from the opening 12 in the width direction D3" means that the neck portion 20 extends linearly in a direction perpendicular to the thickness direction D1 of the sound-absorbing structure 1. Furthermore, at least a portion of the neck portion 20 may have a portion that intersects with the width direction D3. "Intersecting with the width direction D3" means that the extension direction of the neck portion 20 does not coincide with the width direction D3 but is inclined at an angle greater than 0° with respect to the width direction D3. In other words, "intersecting with the width direction D3" means that the neck portion 20 is inclined toward at least one of the thickness direction D1 and the length direction D2 with respect to the width direction D3. For example, the neck portion 20 may extend linearly from the base end to the tip in a direction inclined with respect to the width direction D3, may extend gently curvingly from the base end to the tip in a direction inclined with respect to the width direction D3, or may extend spirally from the base end to the tip. In this way, by having a portion where the neck portion 20 intersects with the width direction D3 of the sound absorbing structure 1, the neck portion 20 can be made longer than the width direction D3 of the sound absorbing structure 1. This makes it possible to reduce tire cavity resonance noise in the lower frequency range.

[0051] The sound absorbing structure 1 configured in this manner can be manufactured by, for example, injection molding, extrusion molding, modeling using a 3D printer, salt coagulation method, or the like.

[0052] As described above, the sound-absorbing structure 1 according to this embodiment includes a box 10 having an opening 12 and a hollow neck portion 20 that is connected to the opening 12 and extends toward the hollow portion 11 of the box 10. This allows the sound-absorbing structure 1 to function as a Helmholtz resonator, and by lengthening the neck portion 20, it is possible to generate Helmholtz resonance at a resonant frequency in the low-frequency range. Furthermore, the opening 12 is formed in the side portion 14 of the box 10, and is oriented in a direction intersecting the thickness direction D1 of the sound-absorbing structure 1. Therefore, the neck portion 20 that is connected to the opening 12 can also be easily extended in a direction intersecting the thickness direction D1 of the sound-absorbing structure 1. In other words, the neck portion 20 can be lengthened without increasing the thickness of the sound-absorbing structure 1. This allows the thickness to be reduced while reducing low-frequency resonance.

[0053] Furthermore, since the side portions 14 extend in a direction intersecting with the direction perpendicular to the thickness direction D1 of the sound absorbing structure 1, the thickness of the sound absorbing structure 1 can be easily reduced.

[0054] Furthermore, since the neck portion 20 extends in a direction perpendicular to the thickness direction D1, it is possible to easily reduce the thickness of the sound absorbing structure 1 while reducing resonance sounds in the low frequency range.

[0055] Furthermore, since the box body 10 has a top portion 13 and a side portion 14 connected to the peripheral portion of the top portion 13 and extending in a direction intersecting the extension direction of the top portion 13, the top portion 13 can cover the upper part of the hollow portion 11.

[0056] Furthermore, since the box 10 has a bottom 15 connected to the side portions 14 and facing the top portion 13, the sound absorbing structure 1 can function as a Helmholtz resonator by itself. Therefore, even if a gap occurs between the sound absorbing structure 1 and the inner cavity 102 of the tire 101, which is the surface to which the sound absorbing structure 1 is attached, the sound absorbing structure 1 can still function as a Helmholtz resonator.

[0057] Furthermore, since the opening 12 is a circular hole, it can be easily designed as a Helmholtz resonator.

[0058] Furthermore, by having the box body 10 have at least one of a Shore A hardness of 40 to 100, 50 to 80, or 60 to 70, and a Shore D hardness of 10 to 70, 10 to 50, or 10 to 40, deformation due to external forces such as centrifugal force and vibration can be suppressed while improving the conformability to the inner cavity 102 of the tire 101, which is the surface to be attached.

[0059] Furthermore, by including an elastomer in the box body 10, deformation due to external forces such as centrifugal force and vibration can be suppressed, while the conformability to the inner cavity 102 of the tire 101, which is the surface to which the box body 10 is attached, can be improved.

[0060] The tire 101 according to this embodiment includes the sound-absorbing structure 1 described above, and is therefore able to reduce tire cavity resonance noise through Helmholtz resonance that occurs in the hollow portion S of the neck portion 20. Moreover, because the opening 12 of the sound-absorbing structure 1 is formed in the side portion 14 of the box body 10, it is possible to reduce the thickness of the sound-absorbing structure 1 while also reducing resonance noise in the low-frequency range. By reducing the thickness of the sound-absorbing structure 1, for example, it is possible to prevent the sound-absorbing structure 1 from interfering with the airflow in the cavity portion 102 of the tire 101, and it is also possible to prevent the sound-absorbing structure 1 from impairing the rotational balance of the tire 101.

[0061] 1 , let F be the frequency of tire cavity resonance sound, c be the speed of light, R be the radius of the cavity portion 102 of the tire 101, r be the radius of the rim 105 of the wheel 104 mounted on the tire 101, and π be the constant of the circumference of the tire. In this case, the frequency of tire cavity resonance sound is calculated by F = c / ((R + r) × π). It is preferable that the sound-absorbing structure 1 be equipped with a Helmholtz resonance structure that generates Helmholtz resonance with a resonance frequency within a range of ±100 Hz of the frequency of tire cavity resonance sound calculated from F = c / ((R + r) × π).

[0062] The Helmholtz resonance structure is a structure that includes the components of a Helmholtz resonator that resonates with sound entering through an opening. In the sound-absorbing structure 1, the Helmholtz resonance structure is formed by the box body 10 and the neck portion 20. That is, in the sound-absorbing structure 1, the non-air-permeable box body 10 extends to the mounting surface 2, and the hollow neck portion 20 is connected to the opening 12 of the box body 10. Therefore, Helmholtz resonance of tire cavity resonance noise can be generated in the hollow portion S of the neck portion 20. The resonant frequency of the sound-absorbing structure 1, which functions as a Helmholtz resonator, varies depending on the extension length of the neck portion 20, the inner diameter of the opening 12, and the like. For example, the longer the extension length of the neck portion 20, the lower the resonant frequency. Furthermore, the smaller the inner diameter of the opening 12, the lower the resonant frequency. Furthermore, the greater the distance between adjacent openings 12, i.e., the width W1, the larger the body volume of the Helmholtz resonator, and the lower the resonant frequency. For this reason, it is preferable that these conditions of the sound-absorbing structure 1 are adjusted so that Helmholtz resonance occurs at a resonance frequency within a range of ±100 Hz of the frequency of tire cavity resonance sound calculated from F = c / ((R + r) × π).

[0063] In this way, by providing a Helmholtz resonance structure that generates Helmholtz resonance at a resonance frequency within a range of ±100 Hz of the frequency of tire cavity resonance noise, tire cavity resonance noise can be reduced.

[0064] 17 is a diagram showing a method for calculating the resonant frequency of the Helmholtz resonance structure. In the figure, each area surrounded by a dashed line represents a Helmholtz resonance structure unit. The resonant frequency of the Helmholtz resonance structure, which resonates with the sound incident from each opening 12, can be adjusted by adjusting the various dimensions of the hollow portion 11 according to this calculation method.

[0065] In FIG. 17 , V denotes the volume of the hollow portion 11 when the hollow portion 11 is divided into Helmholtz resonance structure units. When the openings 12 are arranged in a lattice pattern with a constant period, i.e., when the pitch P between the openings 12 is constant, V is calculated as the volume of a rectangular parallelepiped or cube obtained by multiplying the thickness T of the hollow portion 11 by the square or rectangle that starts at the center of adjacent openings 12 and passes through the midpoints between the openings 12. Note that in this embodiment, the openings 12 are formed in the side portions 14, and the neck portions 20 extend from the side portions 14. Therefore, the thickness T of the hollow portion 11 is the dimension perpendicular to the plane of the paper in FIG. 17 . However, for convenience, FIG. 17 illustrates the thickness T of the hollow portion 11 as the dimension between the side portions 14. When there are multiple ways to draw a rectangle that passes through the midpoints between the openings 12, the rectangle is drawn so that adjacent rectangles do not overlap and so that the area is maximized. Furthermore, when the openings 12 are not arranged periodically but randomly at an unspecified pitch, i.e., when the pitch P between the openings 12 is unspecified, V is calculated as the volume of a polygonal prism obtained by multiplying a polygon having the center of adjacent openings 12 as the origin and the midpoint between the openings 12 as the vertex by the thickness T of the hollow portion 11. In either case, when a neck portion 20 extends into the hollow portion 11, V is calculated by subtracting the volume of the neck portion 20. When a porous sound absorber is disposed in the hollow portion 11, as shown in the third embodiment described later, V is the volume of the hollow portion 11 including the porous sound absorber. α is the area of ​​the opening 12 as viewed from the thickness direction. δ is an opening end correction. For example, if the shape of the opening 12 is circular, δ can be calculated as 0.8 times the diameter of the opening 12. If the shape of the opening 12 is not circular, δ can be calculated as 0.8 times the diameter of a perfect circle having the same area as the area of ​​the opening 12. L is the depth of the opening 12, that is, the extension length of the neck portion 20 (hollow portion).

[0066] Second Embodiment A sound absorbing structure 1A according to a second embodiment will be described with reference to Figure 4. The second embodiment is basically the same as the first embodiment (see Figures 2 and 3), and differs from the first embodiment only in that the box body does not have a bottom but has a flange portion. Therefore, only the differences from the first embodiment will be described below, and a description of the same aspects as the first embodiment will be omitted.

[0067] Fig. 4 is a schematic cross-sectional view of a sound absorbing structure according to the second embodiment. As shown in Fig. 4, a box 10A of the sound absorbing structure 1A according to this embodiment includes a top portion 13, side portions 14, and a flange portion 16. Note that the box 10A does not include a structure corresponding to the bottom portion 15 of the sound absorbing structure 1 according to the first embodiment.

[0068] The flange portion 16 is a portion that forms part of the mounting surface 2. The flange portion 16 extends along the mounting surface 2 from the peripheral edge of the side portion 14 on the side opposite the top portion 13. The width W2 of the flange portion 16 is, for example, approximately 1 mm or more and 20 mm or less. The width W2 is the dimension in the direction away from the side portion 14.

[0069] In the sound absorbing structure 1A, the hollow portion 11 is open downward, and the mounting surface 2 is formed by the end face of the side portion 14 opposite to the top portion 13 and the flange portion 16.

[0070] As described above, the sound absorbing structure 1A according to this embodiment does not have a configuration corresponding to the bottom 15 of the sound absorbing structure 1 according to the first embodiment, but the box 10A has the top portion 13 and the side portions 14 connected to the peripheral edges of the top portion 13 and extending in a direction intersecting the extension direction of the top portion 13, and therefore the sound absorbing structure 1A attached to the inner cavity 102 of the tire 101, which is the attachment surface, can function as a Helmholtz resonator. In other words, the end faces of the side portions 14 opposite to the top portion 13 form the attachment surface 2, and by attaching this attachment surface 2 to the inner cavity 102 of the tire 101, which is the attachment surface, the only open portion of the hollow portion 11 is the opening 12, and the sound absorbing structure 1A functions as a Helmholtz resonator.

[0071] Furthermore, although this sound-absorbing structure 1A does not have a configuration corresponding to the bottom 15 of the sound-absorbing structure 1 of the first embodiment, the box body 10A is provided with a flange portion 16, which makes it possible to easily attach the sound-absorbing structure 1A to the inner cavity portion 102 of the tire 101, which is the surface to be attached.

[0072] Third Embodiment A sound absorbing structure 1B according to a third embodiment will be described with reference to Figure 5. The third embodiment is basically the same as the first embodiment (see Figures 2 and 3), and differs from the first embodiment only in that it further includes a porous sound absorber. Therefore, only the differences from the first embodiment will be described below, and a description of the same aspects as the first embodiment will be omitted.

[0073] Fig. 5 is a schematic cross-sectional view of a sound absorbing structure according to a third embodiment. As shown in Fig. 5, the sound absorbing structure 1B according to this embodiment includes a box body 10, a plurality of neck portions 20, and a porous sound absorbing body 30.

[0074] The porous sound absorber 30 is disposed in the hollow portion 11 of the box body 10. The neck portion 20 is embedded in the porous sound absorber 30. The tip of the neck portion 20 is located inside the porous sound absorber 30.

[0075] The porous sound absorber 30 is formed by foam molding a resin material such as plastic or rubber. Examples of plastic materials include foamed polyurethane. Either hard or soft foamed polyurethane may be used. A common method for producing foamed polyurethane can be used. For example, the porous sound absorber 30 can be obtained by mixing polyol and polyisocyanate with a foaming agent, a foam control agent, a catalyst, etc., filling the mixture into a mold, and allowing it to foam and harden.

[0076] Examples of rubber materials include rubber materials obtained from latex, such as natural rubber (NR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), etc. The porous sound absorber 30 can be obtained by foaming and solidifying these rubber materials.

[0077] The pore diameter of the porous sound absorber 30 is, for example, 1 μm or less, preferably 500 μm or less. The open porosity of the porous sound absorber 30 (the ratio of the total area of ​​the pores on the surface of the porous sound absorber 30 to the area of ​​the porous sound absorber 30) is, for example, approximately 65% ​​to 99%, preferably approximately 80% to 95%. The pore diameter and open porosity can be measured, for example, using a computed tomography (CT scan) device that uses X-rays. The open pore diameter can be calculated by using the average value of the diameters of multiple pores (for example, 100 pores) extracted based on the observed image. The open porosity can be calculated by dividing the total area of ​​all pores extracted based on the observed image by the area of ​​the porous sound absorber.

[0078] As described above, the sound absorbing structure 1B according to this embodiment includes the porous sound absorber 30, and therefore can reduce sounds in the high frequency range.

[0079] (Fourth embodiment) A sound absorbing structure 1C according to a fourth embodiment will be described with reference to Fig. 6. The fourth embodiment is basically the same as the first embodiment (see Figs. 2 and 3), and differs from the first embodiment only in that the neck portion has a fixing portion. Therefore, only the differences from the first embodiment will be described below, and a description of the same aspects as the first embodiment will be omitted.

[0080] Fig. 6 is a schematic cross-sectional view of a sound absorbing structure according to a fourth embodiment. As shown in Fig. 6, a sound absorbing structure 1C according to this embodiment includes a box body 10 and a plurality of neck portions 20C.

[0081] The neck portion 20C has a fixing portion 21C that is fixed to the box body 10 at least at a position away from the opening 12. The neck portion 20C is similar to the neck portion 20 of the first embodiment except for the fixing portion 21C. The position of the fixing portion 21C on the neck portion 20C is not particularly limited, and may be the tip of the neck portion 20C, the center in the extension direction of the neck portion 20C, or the entire area in the extension direction of the neck portion 20C. In addition, the position on the box body 10 to which the fixing portion 21C is fixed is not particularly limited, and may be the top portion 13, the side portion 14, or the bottom portion 15. In this embodiment, the entire area in the extension direction of the neck portion 20C is the fixing portion 21C that is fixed to the bottom portion 15. Furthermore, the neck portion 20C extends along the bottom 15 in a direction parallel to the width direction D3 and the length direction D2, and the tip of the neck portion 20C is oriented in a direction parallel to the width direction D3 and the length direction D2, so that the hollow portion S of the neck portion 20C is an open end exposed to the hollow portion 11. The fixing portion 21C can be fixed to the box body 10C by, for example, integral molding, adhesion, welding, or the like.

[0082] As described above, in the sound absorbing structure 1C according to this embodiment, the neck portion 20C has the fixing portion 21C that fixes it to the box body 10 at least at a position spaced apart from the opening 12, and therefore it is possible to suppress movement of the neck portion 20C relative to the box body 10. Therefore, for example, when an external force such as centrifugal force or vibration acts on the sound absorbing structure 1C, it is possible to suppress excessive displacement of the neck portion 20C relative to the box body 10.

[0083] Fifth Embodiment A sound absorbing structure 1D according to a fifth embodiment will be described with reference to Figure 7. The fifth embodiment is basically the same as the first embodiment (see Figures 2 and 3), and differs from the first embodiment only in that the hollow portion of the box body is divided. Therefore, only the differences from the first embodiment will be described below, and a description of the same aspects as the first embodiment will be omitted.

[0084] Fig. 7 is a schematic cross-sectional view of a sound absorbing structure according to a fifth embodiment. Neck portions are not shown in Fig. 7. As shown in Fig. 7, a sound absorbing structure 1D according to this embodiment includes a box body 10D and a plurality of neck portions 20 (see Fig. 3). The box body 10D includes a top portion 13, side portions 14, a bottom portion 15, and a plurality of partition walls 17.

[0085] Each of the partition walls 17 is connected to the top portion 13, the side portions 14, and the bottom portion 15 and divides the hollow portion 11 into two small spaces 11a. For example, each of the partition walls 17 divides the hollow portion 11 in the longitudinal direction D2. When four partition walls 17 are provided as shown in FIG. 7 , the hollow portion 11 is divided into five small spaces 11a by the four partition walls 17. The partition walls 17 are connected to the top portion 13, the side portions 14, and the bottom portion 15 so that the two divided small spaces 11a are not connected to each other. Therefore, the two small spaces 11a divided by the partition walls 17 are independent of each other. Furthermore, each of the partition walls 17 divides the hollow portion 11 so that at least one opening 12 is connected to each of the divided small spaces 11a. In this case, each of the plurality of partition walls 17 may divide the hollow portion 11 so that each of the partitioned small spaces 11 a is connected to one opening 12. The partition wall 17 is formed, for example, in a flat plate shape extending along the thickness direction D1 and the width direction D3.

[0086] As described above, in this sound-absorbing structure 1D, the hollow portion 11 of the box body 10D is divided into two small spaces 11a by a partition wall 17, and at least one opening 12 is connected to each of the two small spaces 11a, so that each of the two small spaces 11a can function as a Helmholtz resonator while increasing the rigidity of the sound-absorbing structure 1D.

[0087] Furthermore, by providing one opening 12 in communication with each of the two small spaces 11a, the sound absorbing structure 1D can be divided into Helmholtz resonator units.

[0088] Sixth Embodiment A sound absorbing structure 1E according to a sixth embodiment will be described with reference to Figures 8 and 9. The sixth embodiment is basically the same as the fifth embodiment (see Figure 7), and differs from the fifth embodiment only in the configuration of the partition walls, the top portion, and the side portions. Therefore, only the differences from the fifth embodiment will be described below, and a description of the same aspects as the fifth embodiment will be omitted.

[0089] Fig. 8 is a schematic perspective view of a sound absorbing structure according to a sixth embodiment. Fig. 9 is a schematic cross-sectional view taken along line IX-IX in Fig. 8. Note that neck portions are not shown in Fig. 9. As shown in Figs. 8 and 9, a sound absorbing structure 1E according to this embodiment includes a box body 10E and a plurality of neck portions 20 (see Fig. 3). The box body 10E includes a top portion 13E, side portions 14E, a bottom portion 15, and a plurality of partition walls 17E.

[0090] Each of the partition walls 17E has a first partition wall portion 17a and a second partition wall portion 17b. The first partition wall portion 17a is located on one side of the two small spaces 11a separated by each of the partition walls 17E, and the second partition wall portion 17b is located on the other side of the two small spaces 11a separated by each of the partition walls 17E.

[0091] The top portion 13E and the side portions 14E are divided by the first partition wall portion 17a and the second partition wall portion 17b. That is, the top portion 13E is divided into a plurality of small top portions 13a by the first partition wall portion 17a and the second partition wall portion 17b that respectively constitute the plurality of partition walls 17E. The side portions 14E are divided into a plurality of small side portions 14a by the first partition wall portion 17a and the second partition wall portion 17b that respectively constitute the plurality of partition walls 17E. The bottom portion 15 is not divided by the first partition wall portion 17a and the second partition wall portion 17b.

[0092] The first partition wall 17a and the second partition wall 17b are arranged in a V-shape such that the distance between them increases toward the ceiling 13E. If the portion of the bottom 15 forming the small space 11a is defined as the bottom 15a, the length of the small ceiling 13a in the longitudinal direction D2 is shorter than the length of the bottom 15a in the longitudinal direction D2. The first partition wall 17a and the second partition wall 17b may be separate from each other, or may be connected to each other at the end opposite the ceiling 13E. In other words, the first partition wall 17a and the second partition wall 17b may be indirectly connected via the bottom 15, or may be directly connected.

[0093] As described above, in this sound absorbing structure 1E, the top portion 13E and the side portion 14E are divided by the first partition wall portion 17a and the second partition wall portion 17b, which makes it easier to curve or bend the sound absorbing structure 1E, thereby further improving the conformability to the inner cavity portion 102 of the tire 101, which is the surface to which the sound absorbing structure 1E is attached.

[0094] Furthermore, since the first partition wall portion 17a and the second partition wall portion 17b are arranged so that the distance between them increases toward the top portion 13E, it becomes easier to curve or bend the sound-absorbing structure 1E so that the top portion 13E side is facing inward.

[0095] Furthermore, since the length of the small ceiling portion 13a in the longitudinal direction D2 is shorter than the length of the bottom portion 15a in the longitudinal direction D2, it becomes easier to curve or bend the sound absorbing structure 1E so that the ceiling portion 13E side faces inward.

[0096] Furthermore, since the first partition wall portion 17a and the second partition wall portion 17b are connected to each other at the end opposite the top portion 13E, it is possible to prevent the sound absorbing structure 1E from becoming too large while allowing the sound absorbing structure 1E to bend or curve.

[0097] Seventh Embodiment A sound absorbing structure 1F according to a seventh embodiment will be described with reference to Figures 10 to 12. The seventh embodiment is basically the same as the first embodiment (see Figures 2 and 3), and differs from the first embodiment only in the shape of the openings. Therefore, only the differences from the first embodiment will be described below, and a description of the same aspects as the first embodiment will be omitted.

[0098] Fig. 10 is a schematic perspective view of a sound absorbing structure according to a seventh embodiment. Fig. 11 is a schematic cross-sectional view taken along line XI-XI in Fig. 10. Fig. 12 is a schematic cross-sectional view taken along line XII-XII in Fig. 10. As shown in Figs. 10 to 12, a sound absorbing structure 1F according to this embodiment includes a box body 10F and a plurality of neck portions 20F.

[0099] The box body 10F includes a top portion 13, side portions 14F, and a bottom portion 15. The side portions 14F are formed with a plurality of openings 12F that communicate with the hollow portion 11 of the box body 10F. The side portions 14F are similar to the side portions 14 of the first embodiment, except that the openings 12F are formed instead of the openings 12. The side portions 14F have a pair of long sides 141F and a pair of short sides 142F that correspond to the pair of long sides 141 and the pair of short sides 142 of the first embodiment. The plurality of openings 12F are formed in one of the long sides 141F and are aligned in the longitudinal direction D2. The long side portion 141F in which the plurality of openings 12F are formed is referred to as the opening-forming side portion 143F.

[0100] The opening 12F is a linear slit that penetrates the opening-forming side portion 143F. The slit that is the opening 12F extends linearly in the thickness direction D1 across the entire area of ​​the opening-forming side portion 143F in the thickness direction D1.

[0101] The neck portion 20F is connected to the slit that is the opening 12F and extends from the opening-forming side portion 143F toward the hollow portion 11. The neck portion 20F is similar to the neck portion 20 of the first embodiment, except that it is connected to the slit that is the opening 12F.

[0102] The shape of the neck portion 20F is not particularly limited. For example, the neck portion 20F may extend linearly from the opening 12F in the width direction D3. Alternatively, the neck portion 20F may extend in a bent or curved manner. Alternatively, at least a portion of the neck portion 20F may have a portion that intersects with the width direction D3. For example, the neck portion 20F may extend linearly from the opening 12F in the width direction D3, then bend or curve in an L-shape or a J-shape, and extend linearly in the longitudinal direction D2.

[0103] The sound absorbing structure 1F configured in this manner can be manufactured by, for example, injection molding, extrusion molding, 3D printer modeling, salt coagulation, etc. For example, because the slits that are the openings 12F extend linearly in the thickness direction D1 across the entire area of ​​the opening-forming side portions 143F in the thickness direction D1, the sound absorbing structure 1F excluding the top portion 13, the bottom portion 15, and the long side portions 141F that face the opening-forming side portions 143F can be manufactured by extrusion molding. Then, the sound absorbing structure 1F excluding the top portion 13, the bottom portion 15, and the long side portions 141F that face the opening-forming side portions 143F can be manufactured by joining separately manufactured top portion 13, bottom portion 15, and long side portions 141F that face the opening-forming side portions 143F to the sound absorbing structure 1F excluding the top portion 13, the bottom portion 15, and the long side portions 141F that face the opening-forming side portions 143F. Alternatively, the sound absorbing structure 1F can be manufactured by continuously extruding a structure having the same cross section as the sound absorbing structure 1F, excluding the top portion 13, the bottom portion 15, and the long side portion 141F opposite the opening-forming side portion 143F, in the thickness direction D1, cutting the extruded structure to a predetermined length in the thickness direction D1, and joining the separately prepared top portion 13, the bottom portion 15, and the long side portion 141F opposite the opening-forming side portion 143F to the cut structure.

[0104] As described above, in the sound absorbing structure 1F, the openings 12F are linearly extending slits, which makes it possible to easily manufacture the sound absorbing structure 1F.

[0105] Eighth Embodiment A sound absorbing structure 1G according to an eighth embodiment will be described with reference to Figures 13 and 14. The eighth embodiment is basically the same as the seventh embodiment (see Figures 10 to 12), and differs from the seventh embodiment only in the extension direction of the slits, which are openings. Therefore, only the differences from the seventh embodiment will be described below, and a description of the same aspects as the seventh embodiment will be omitted.

[0106] Fig. 13 is a schematic perspective view of a sound absorbing structure according to an eighth embodiment. Fig. 14 is a schematic cross-sectional view taken along line XIV-XIV in Fig. 13. As shown in Figs. 13 and 14, a sound absorbing structure 1G according to this embodiment includes a box body 10G and one neck portion 20G.

[0107] The box 10G includes a top portion 13, side portions 14G, and a bottom portion 15. The side portion 14G has one opening 12G formed therein, which is connected to the hollow portion 11 of the box 10G. The side portion 14G is similar to the side portion 14F of the seventh embodiment, except that the opening 12G is formed instead of the opening 12F. The side portion 14G has a pair of long sides 141G and a pair of short sides 142G, which correspond to the pair of long sides 141F and the pair of short sides 142F of the seventh embodiment. The opening 12G is formed in one of the long sides 141G. The long side portion 141G in which the opening 12G is formed is referred to as the opening-forming side portion 143G.

[0108] The opening 12G is a linear slit that penetrates the opening-forming side portion 143G. The slit that is the opening 12G extends linearly in the length direction D2 over the entire area of ​​the opening-forming side portion 143G in the length direction D2.

[0109] The neck portion 20G is connected to the slit that is the opening 12G and extends from the opening-forming side portion 143G toward the hollow portion 11. The neck portion 20G is similar to the neck portion 20F of the seventh embodiment, except that it is connected to the slit that is the opening 12G.

[0110] The sound-absorbing structure 1G configured in this manner can be manufactured by, for example, injection molding, extrusion molding, 3D printer modeling, salt coagulation, or the like. For example, because the slits that form the openings 12G extend linearly in the longitudinal direction D2 across the entire area of ​​the opening-forming side portion 143G in the longitudinal direction D2, the sound-absorbing structure 1G excluding the pair of short side portions 142G can be manufactured by extrusion molding. The sound-absorbing structure 1G can then be manufactured by joining a pair of separately manufactured short side portions 142G to the sound-absorbing structure 1G excluding the pair of short side portions 142G. Alternatively, the sound-absorbing structure 1G can be manufactured by continuously extruding a structure having the same cross section as the sound-absorbing structure 1G excluding the pair of short side portions 142G in the longitudinal direction D2, cutting the extruded structure to a predetermined length in the longitudinal direction D2, and joining a pair of separately manufactured short side portions 142G to the cut structure.

[0111] Ninth Embodiment A sound absorbing structure 1H according to a ninth embodiment will be described with reference to Figure 15. The ninth embodiment is basically the same as the sixth embodiment (see Figures 8 and 9), and differs from the sixth embodiment only in that the opening has a shape similar to that of the seventh embodiment. Therefore, only the differences from the sixth embodiment will be described below, and a description of the same aspects as the sixth embodiment will be omitted.

[0112] Fig. 15 is a schematic perspective view of a sound absorbing structure according to the ninth embodiment. As shown in Fig. 15, a sound absorbing structure 1H according to this embodiment includes a box body 10H and a plurality of neck portions 20F (see Figs. 11 and 12) similar to those of the seventh embodiment. The box body 10H includes a top portion 13E, side portions 14H, a bottom portion 15, and a plurality of partition walls 17E (see Figs. 8 and 9). Each of the plurality of partition walls 17E includes a first partition wall portion 17a and a second partition wall portion 17b.

[0113] A plurality of openings 12H are formed in the side portion 14H. As in the seventh embodiment, the openings 12H are linear slits that extend linearly in the thickness direction D1 across the entire area of ​​the side portion 14H in the thickness direction D1. The neck portion 20F is connected to the slits that are the openings 12H and extends from the side portion 14H toward the hollow portion 11.

[0114] The present disclosure is not limited to the above-described embodiments, and modifications can be made as appropriate without departing from the spirit of the present disclosure.

[0115] For example, when a plurality of openings and necks are provided, the frequencies of Helmholtz resonances generated in at least two of the necks may be different from each other. By making the frequencies of Helmholtz resonances generated in at least two of the necks different from each other, tire cavity resonance noise can be reduced over a wide frequency band.

[0116] Furthermore, for example, the sound absorbing structure may be formed in a flat plate shape or a curved shape. For example, as in the sound absorbing structure 1I shown in Fig. 16, the sound absorbing structure may be formed in a shape that is curved in an arc along the inner cavity of the tire. Fig. 16 is a schematic side view showing a modified sound absorbing structure. In this way, the sound absorbing structure is curved in an arc, which improves ease of attachment to the inner cavity of the tire.

[0117] Furthermore, for example, when a plurality of sound absorbing structures are attached to a tire, two or more sound absorbing structures that generate Helmholtz resonances with mutually different resonance frequencies may be attached to the tire.

[0118] Furthermore, for example, the sound absorbing structure may further include a hollow outer neck portion that communicates with an opening formed in the box and extends to the outside of the box (the side opposite the hollow portion) so as to extend the neck portion outside the box. In this case, the resonant frequency of the sound absorbing structure can be adjusted by adjusting the total length of the neck portion and the outer neck portion.

[0119] Furthermore, for example, in the above embodiment, the sound-absorbing structure has been described as a sound-absorbing structure for a tire that is attached to the tire cavity portion in order to reduce tire cavity resonance noise, but the use of the sound-absorbing structure is not particularly limited.

[0120] Furthermore, for example, in the above embodiment, the box body has been described as having a top portion, side portions, and a bottom portion. However, the box body may have any shape and structure as long as it has side portions with openings formed therein. In other words, as long as the box body has side portions with openings formed therein, it is possible to reduce low-frequency resonance noise while making it easier to reduce the thickness of the box body, regardless of the shape and structure of the box body. Therefore, the box body may be formed, for example, in a cylindrical shape. When the box body is formed in a cylindrical shape, for example, an opening communicating with the neck portion may be formed in at least one of the opposing end portions, and the box body may be attached to the inner cavity of the tire so that at least one of the end portions becomes a side portion of the box body.

[0121] The gist of the present disclosure is as follows: [1] to

[18] . [1] A sound-absorbing structure comprising a box body having an opening and a hollow neck portion communicating with the opening and extending toward a hollow portion of the box body, the opening being formed in a side portion of the box body. [2] The sound-absorbing structure according to [1], wherein the side portion extends in a direction intersecting a direction perpendicular to a thickness direction of the sound-absorbing structure. [3] The sound-absorbing structure according to [1] or [2], wherein the neck portion extends in a direction perpendicular to the thickness direction. [4] The sound-absorbing structure according to any one of [1] to [3], wherein the neck portion has a fixing portion that is fixed to the box body at least at a position spaced apart from the opening. [5] The sound-absorbing structure according to any one of [1] to [4], wherein the opening is a circular hole. [6] The sound-absorbing structure according to any one of [1] to [5], wherein the opening is a linear slit. [7] The sound absorbing structure according to any one of [1] to [6], further comprising a porous sound absorbing material housed in the hollow portion of the box body. [8] The sound absorbing structure according to any one of [1] to [7], wherein the box body has at least one of a Shore A hardness of 80 to 100 and a Shore D hardness of 30 to 70. [9] The sound absorbing structure according to any one of [1] to [8], wherein the box body comprises an elastomer.

[10] The sound absorbing structure according to any one of [1] to [9], wherein the box body has a top portion, and the side portions are connected to a peripheral edge of the top portion and extend in a direction intersecting the extension direction of the top portion.

[11] The sound absorbing structure according to

[10] , wherein the box body further has a bottom portion connected to the side portions and facing the top portion.

[12] The sound absorbing structure according to

[11] or

[12] , wherein the box body has a plurality of the openings and a partition wall connected to the top and side portions and dividing the hollow portion into two small spaces, the partition wall dividing the hollow portion so that at least one of the openings communicates with each of the two small spaces.

[13] The sound absorbing structure according to

[12] , wherein the partition wall divides the hollow portion so that one of the openings communicates with each of the two small spaces.

[14] The sound absorbing structure according to

[12] or

[13] , wherein the partition wall has a first partition wall portion located on one side of the two small spaces and a second partition wall portion located on the other side of the two small spaces, and the top portion and the side portion are divided by the first partition wall portion and the second partition wall portion.

[15] The sound absorbing structure according to

[14] , wherein the first partition wall portion and the second partition wall portion are arranged so that the distance between them increases toward the top portion.

[16] The sound absorbing structure according to

[14] or

[15] , wherein the first partition wall portion and the second partition wall portion are connected to each other at an end portion opposite the top portion.

[17] A tire comprising the sound absorbing structure according to any one of [1] to

[16] attached to an inner cavity portion.

[18] The tire according to

[17] , wherein the sound absorbing structure comprises a Helmholtz resonance structure that generates a Helmholtz resonance with a resonance frequency within a range of ±100 Hz of the frequency of tire cavity resonance sound calculated from F = c / ((R + r) × π), where F is the frequency of tire cavity resonance sound, c is the speed of light, R is the radius of the tire cavity, r is the radius of the rim of a wheel mounted on the tire, and π is the ratio of the circumference of a circle to its circumference.

[0122] 1...Sound absorption structure, 1A...Sound absorption structure, 1B...Sound absorption structure, 1C...Sound absorption structure, 1D...Sound absorption structure, 1E...Sound absorption structure, 1F...Sound absorption structure, 1G...Sound absorption Structure, 1H... Sound absorbing structure, 1I... Sound absorbing structure, 2... Mounting surface, 3... Top surface, 4... Adhesive sheet, 10... Box body, 10A... Box body, 10C... Box body, 10D... Box body , 10E...box body, 10F...box body, 10G...box body, 10H...box body, 11...hollow part, 11a...small space, 12...opening, 12F...opening, 12G...opening, 12H ...opening, 13...top, 13a...small top, 13E...top, 14...side, 141...long side, 142...short side, 143...opening forming side, 14a...small side, 14 E...side portion, 14F...side portion, 141F...long side portion, 142F...short side portion, 143F...opening forming side portion, 14G...side portion, 141G...long side portion, 142G...short side portion, 143G...opening forming side portion, 14H...side portion, 15...bottom, 15a...bottom, 16...flange portion, 17...compartment wall, 17a...first partition wall portion, 17b...second partition wall portion, 17E...compartment wall, 20...neck portion, 20C...neck portion, 20F...neck portion, 20G...neck portion, 21C...fixing portion, 30...porous sound absorbing body, 101...tire, 102...inner cavity portion, 103...tread, 104...wheel, 105...rim, D1...thickness direction, D2...length direction, D3...width direction, S...hollow portion.

Claims

1. A box having an opening; a hollow neck portion communicating with the opening and extending toward the hollow portion of the box body; The opening is formed in a side portion of the box body, The neck portion extends along the wall of the box. Sound absorbing structure.

2. The box body has a bottom portion disposed on the side of the mounting target surface to which the sound absorbing structure is attached, The neck portion extends along the base portion. The sound absorbing structure according to claim 1 .

3. The neck portion is disposed on the bottom portion.

3. The sound absorbing structure according to claim 2.

4. The side portion extends in a direction intersecting a direction perpendicular to a thickness direction of the sound absorbing structure. The sound absorbing structure according to claim 1 .

5. The neck portion extends in a direction perpendicular to a thickness direction of the sound absorbing structure. The sound absorbing structure according to claim 1 .

6. The neck portion has a fixing portion fixed to the box body at least at a position spaced from the opening. The sound absorbing structure according to claim 1 .

7. The opening is a circular hole. The sound absorbing structure according to claim 1 .

8. The opening is a linearly extending slit. The sound absorbing structure according to claim 1 .

9. The sound absorbing device further includes a porous sound absorbing body accommodated in the hollow portion of the box body. The sound absorbing structure according to claim 1 .

10. The box has at least one of a Shore A hardness of 40 or more and 100 or less and a Shore D hardness of 10 or more and 70 or less. The sound absorbing structure according to claim 1 .

11. The box includes an elastomer. The sound absorbing structure according to claim 1 .

12. The box body has a top portion, The side portion is connected to the peripheral edge portion of the top portion and extends in a direction intersecting with the extension direction of the top portion. The sound absorbing structure according to claim 1 .

13. The box body further has a bottom portion connected to the side portion and facing the top portion.

13. A sound absorbing structure as claimed in claim 12.

14. The box body has a plurality of the openings and a partition wall connected to the top portion and the side portion to divide the hollow portion into two small spaces, The partition wall divides the hollow portion such that at least one of the openings communicates with each of the two small spaces.

13. A sound absorbing structure as claimed in claim 12.

15. The partition wall divides the hollow portion such that one of the openings communicates with each of the two small spaces.

15. A sound absorbing structure as claimed in claim 14.

16. The partition wall has a first partition wall portion located on one side of the two small spaces and a second partition wall portion located on the other side of the two small spaces, The top portion and the side portion are divided by the first partition wall portion and the second partition wall portion.

15. A sound absorbing structure as claimed in claim 14.

17. The first partition wall portion and the second partition wall portion are disposed such that a distance therebetween increases toward the top portion.

17. A sound absorbing structure according to claim 16.

18. The first partition wall portion and the second partition wall portion are connected to each other at an end portion opposite to the top portion.

17. A sound absorbing structure according to claim 16.

19. The box body is formed into a cylindrically extending shape. The sound absorbing structure according to claim 1 .

20. The sound absorbing structure according to any one of claims 1 to 19 is attached to an inner cavity. tire.

21. When the frequency of tire cavity resonance sound is F, the speed of light is c, the radius of the tire cavity portion is R, the radius of the rim of a wheel mounted on the tire is r, and pi is π, the sound absorbing structure is provided with a Helmholtz resonance structure that generates a Helmholtz resonance having a resonance frequency within a range of ±100 Hz of the frequency of tire cavity resonance sound calculated from F = c / ((R + r) × π).

21. The tire of claim 20.